In the field of printing duplication, it has been desired to improve the working efficiency in steps of photomechanical process so as to cope with the diversity and complexity of prints.
More specifically in contact works, working efficiency has been improved by conducting photomechanical process in a brighter environment. Therefore, it has been intended to develop silver halide photographic materials for photomechanical use which are capable of being handled in substantially bright environment, and to develop a printer for exposing such photographic materials.
Silver halide photographic materials to be handled in a bright environment means those photographic materials which allow the use of light rays of 400 nm or longer in wavelength, and not containing an ultraviolet ray component, as a safelight.
As processes for preparing light-sensitive materials having a low sensitivity to visible light, there are generally known a process of forming grains by adding a large quantity of a rhodium salt, an iridium salt or a cupric chloride to a silver halide emulsion and a process of adding an organic desensitizing agent such as pinacryptol yellow, phenosafranine, etc.
A particularly preferable process for preparing light-sensitive materials with a super-low sensitivity to visible light is the process of incorporating a water-soluble rhodium salt in a silver halide emulsion. For example, Japanese Patent Application (OPI) Nos. 125734/81 and 149030/81 (the term "OPI" as used herein means an "unexamined published application") disclose a process of incorporating a rhodium salt in an amount as much as 10.sup.-3 to 10.sup.-5 mol per mol of silver.
However, when sufficient handling properties in a bright environment are tried to be obtained by only the addition of rhodium salts, the sensitivity to UV rays is also decreased with the decrease in sensitivity to visible light. In addition, a low contrast photographic characteristic curve results.
In addition, silver salts containing a large quantity of rhodium salt, as described above, have the disadvantage that they tend to be rendered low contrast with respect to the photographic properties thereof, during storage.
In order to avoid these problems, Japanese Patent Application (OPI) No. 193447/84 discloses a process of decreasing the amount of a rhodium salt to be added, by mordanting a dye, having an absorption in the visible light region, to an upper layer of a silver halide emulsion layer. However, this process is disadvantageous in that, in reduction processing, which is often employed in this field for correcting images after development processing of light-sensitive materials for photomechanical process, dyes once decolored in the development processing again acquire their colors.
Conventionally developed silver halide photographic materials which can be handled in a substantially bright environment must be exposed by a printer having an intense light source rich in an ultraviolet ray component, such as a super-high pressurem mercury lamp or a metal halide lamp, due to the super-low sensitivity of the photographic materials.